CN108985643A - The methodology of the heat supply of Gas-steam Combined Cycle cogeneration units and fuel used to generate electricity cost - Google Patents

Abstract

The invention discloses the methodologies of a kind of heat supply of Gas-steam Combined Cycle cogeneration units and fuel used to generate electricity cost, for rationally determining for two aspect proportion in fuel cost of heat and generating power.Its technical solution is: it carries out quantification treatment to the utility value of various energy from the angle of different-energy grade, and the energy grade quantization parameter for the heat that steam and flue gas contain is determined by following formula:The present invention has comprehensively considered the thermoelectricity load combination condition in the cascaded utilization of energy relationship and operational process of Gas-steam Combined Cycle under specific operating condition, can reasonable distribution fuel cost to for the aspect of heat and generating power two, provide reference frame to formulate heat supply and generating price.

Description

Analysis of fuel costs for heating and power generation of gas-steam combined cycle cogeneration units spread method

technical field

The invention relates to a method for rationally allocating fuel costs for heat supply and power generation of gas-steam combined cycle heat and power cogeneration units, belonging to the technical field of heat and power cogeneration.

Background technique

The gas-steam combined cycle system is based on the cascade utilization of energy, which has the advantages of high energy utilization rate and good environmental protection. In the gas-steam combined cycle power generation process, the exhaust gas temperature of the gas turbine is often high, and the boiler needs to recover waste heat to reduce heat loss. At the same time, in the combined heat and power unit of the steam cycle, the steam first enters the steam turbine to do work to ensure the power generation, and then part of the steam is extracted to provide heat users. Therefore, in the gas-steam combined cycle heat and power cogeneration unit, the two energy products of electricity and heat are different in energy grade; Grade; the grade of heat contained in the working medium steam entering the steam turbine for work is higher than that contained in the heat carrier steam entering the heating network for heating.

Due to the particularity of cogeneration unit production itself, how to reasonably and effectively determine the heat and power allocation ratio in cogeneration is still a controversial and worthwhile topic so far. A reasonable heat and power sharing ratio should be able to more comprehensively reflect the actual situation of energy conversion, utilization and loss in the process of cogeneration, and achieve the rational use of energy as much as possible.

In the traditional calculation method of heat and electricity allocation ratio, the heat method treats electric energy and heat energy of different qualities as equivalent, only considers the numerical value of energy, and ignores the important factor of quality. When calculating the heat and electricity allocation ratio, it is considered There is no cold source and irreversible loss in the thermal power generation part, and this part of the loss is all used for external heat supply. Therefore, this method attributes both cold source and irreversible loss to the heating party, which cannot reasonably reflect the actual conversion process of energy in the unit.

The working capacity method considers the influence of insufficient work done by the heating steam in the steam turbine, and pays attention to the difference in the grade of the heating steam under different pressures and temperatures. The high-quality high-price, low-quality low-price heat and electricity sharing method encourages users to actively improve the production process and reduce the steam pressure and temperature as much as possible, which will promote the increase of thermal power generation and the economic efficiency of thermal power plants. However, this method attributes the cold source and irreversible loss of thermal power generation to the power generation side, which cannot reasonably reflect the actual conversion process of energy in the unit.

The functioning ability method is only used to measure the difference in mass of energy, completely ignoring the thermal user's contribution to Applications. When the steam turbine exhaust parameters are close to the environmental parameters, the calculated apportionment ratio is close to the actual enthalpy drop method. Therefore, this method cannot reasonably reflect the actual conversion process of energy in the unit.

In view of this, in order to overcome the shortcomings of the above-mentioned traditional methods, consider at the same time: in the gas-steam combined cycle cogeneration unit, the two energy products of electricity and heat are different in energy grade; the working medium flue gas of the gas cycle contains The grade of heat contained in the working medium steam of the steam cycle is higher than that of the heat contained in the working medium steam of the steam cycle; the heat contained in the working medium steam entering the steam turbine is higher than the heat contained in the heat carrier steam entering the heating network for heating. The present invention proposes An apportionment method for rationally allocating fuel costs for heating and power generation of gas-steam combined cycle cogeneration units.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a fuel cost apportionment method for heating and power generation of a gas-steam combined cycle heat and power cogeneration unit.

Technical scheme of the present invention is as follows:

The gas-steam combined cycle cogeneration unit heating and power generation fuel cost apportionment method of the present invention is characterized in that it comprises the following steps:

1) According to the actual operation of the unit, consult the water vapor property parameter manual, and determine the values of the parameters required for calculation, including the ambient temperature, the enthalpy value, entropy value and heat supply of each section of heating and extraction steam, and the power generation of the gas turbine and steam turbine amount, etc.;

2) Assuming that the unit has n stages of heating and extraction steam, determine the energy grade quantification coefficient of the heat contained in the i-th heating extraction steam and the total heat supply and extraction energy grade quantization coefficient:

In the formula, for the heating and extraction of the i-th section, A _Ri is its energy grade quantization coefficient; ΔE _i is its energy utilization process Change, kJ/kg; ΔH _i is the change of enthalpy in the process of energy utilization, kJ/kg; T ₀ is the ambient temperature, K; ΔS _i is the change of entropy in the process of energy utilization, kJ/kg K; Q _Ri is the heat supply of steam for heating and extraction, kJ; A _R is the energy grade quantification coefficient of steam for heating and extraction; Q _R is the heat supply of steam for heating and extraction, kJ;

3) Determine the weight proportional coefficient of heating and power generation in the gas-steam combined cycle system:

X _qR ＝A _R Q _R /A _f Q _cogf

X _qP ＝A _P Q _P /A _f Q _cogf

In the formula, X _qR is the weight proportional coefficient of heating energy consumption in the system; X _qP is the weight proportional coefficient of power generation energy consumption in the system; A _f is the energy grade quantization coefficient of fuel; A _P is the energy grade quantization coefficient of electric energy; Q _cogf is the quantity of fuel combustion and chemical energy converted into heat energy, kJ; Q _P is the energy of generating electric energy, kJ;

4) Determine the final heat and electricity allocation ratio. The final heat and electricity allocation ratio is the ratio of the weight proportional coefficient of the energy consumed by heating in the system to the sum of the weight proportional coefficients of the energy consumed by power generation. The expression is as follows:

In the formula, β _tp is the final thermoelectric sharing ratio; ΔQ is the total energy loss, kJ; ΔQ _r is the energy loss allocated to the heat side, kJ.

Further, the total energy loss ΔQ includes losses as follows:

ΔQ＝Δ(A _f Q _cogf )+Δ(A ₃ Q ₃ )+Δ(A _b Q _b )+Δ(A ₄ Q ₄ )+Δ(A _r Q _r )

In the formula, Δ(A _f Q _cogf ) is the energy loss of natural gas during combustion; Δ(A ₃ Q ₃ ) is the energy loss of flue gas in the process of gas turbine doing work; Δ(A _b Q _b ) is the energy loss of waste heat boiler Energy loss; Δ(A ₄ Q ₄ ) is the energy loss of steam in the process of steam turbine doing work; Δ(A _r Q _r ) is the energy loss in the process of heating and extracting steam to heat users, and the unit is kJ.

The total energy loss ΔQ is distributed between the heating side and the power generation side according to the ratio of X _qR to X _qP :

ΔQ＝ΔQ _r +ΔQ _p

In the formula, ΔQ _p is the energy loss allocated to the generator, kJ.

Furthermore, based on the perspective of thermodynamic cycle, the value of mechanical work is the largest, so the energy grade quantization coefficient _AP of electrical energy is agreed to be 1; since the fuel contains chemical energy, its The value is not much different from the lower calorific value, so the grade coefficient A _f of the fuel can also be considered to be the largest, which is set to 1.

Starting from the energy grade, the present invention combines the two aspects of energy quality and quantity to determine a clear theoretical basis, promote the comprehensive utilization of energy cascades, use energy according to quality, and calculate relatively simple. The energy cascade utilization relationship of the steam combined cycle and the thermal and electrical load combination conditions under specific working conditions in the operation process can reasonably allocate fuel costs to heating and power generation, and provide a reference for formulating heating and power generation prices.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a diagram of the change of heat and electricity sharing ratio under the condition of G100-M50L35;

Figure 2 is a diagram of the change of the heat and electricity sharing ratio under the condition of G100-H55L35;

Fig. 3 is a graph showing the change of heat and electricity sharing ratio under the condition of G100-H55M55;

Figure 4 is a schematic diagram of the gas-steam combined cycle heat and electricity cogeneration energy cascade utilization process.

Each label in the figure: A _f , fuel energy grade quantification coefficient; Q _cogf , fuel combustion, the amount of chemical energy converted into heat energy; Δ(A _f Q _cogf ), energy loss of natural gas during combustion; Δ(A ₃ Q ₃ ), the energy loss of flue gas in the process of gas turbine work; Δ(A _b Q _b ), the energy loss in waste heat boiler; Δ(A ₄ Q ₄ ), the energy loss of steam in the process of steam turbine work; Δ(A _r Q _r ), the energy loss in the process of transporting heating extraction steam to heat users.

Symbols used in this paper: A _R , the energy grade quantification coefficient of heating and extraction; A _P , the energy grade quantization coefficient of electric energy; Q _R , the heat of heating and extraction; Q _P , the energy of generating electric energy; ΔQ, the total energy Loss; ΔQ _r , the energy loss allocated to the heating party; ΔQ _p , the energy loss allocated to the power generation side; β _tp , the heat and electricity sharing ratio.

Detailed ways

The present invention is used for the apportionment calculation method of the fuel cost of the gas-steam combined cycle heat and power cogeneration unit for heating and power generation, and the specific steps are as follows:

1) According to the actual operation of the unit, consult the water vapor property parameter manual, and determine the values of the parameters required for calculation, including the ambient temperature, the enthalpy value, entropy value and heat supply of each section of heating and extraction steam, and the power generation of the gas turbine and steam turbine amount, etc.;

2) As shown in Figure 4, in the gas-steam combined cycle cogeneration unit, natural gas is burned in the combustion chamber to generate flue gas, which enters the gas turbine to drive the blades to rotate to generate electricity, and the flue gas that has completed the work enters the waste heat boiler to transfer heat energy Into the steam, the steam enters the steam turbine to generate power, and part of the steam is extracted to the heat user.

3) Assuming that the unit has n stages of heating and extraction steam, determine the energy grade quantification coefficient of the heat contained in the i-th heating extraction steam and the total energy grade quantization coefficient of heating and extraction steam:

In the formula, for the heating and extraction of the i-th section, A _Ri is its energy grade quantization coefficient; ΔE _i is its energy utilization process Change, kJ/kg; ΔH _i is the change of enthalpy in the process of energy utilization, kJ/kg; T ₀ is the ambient temperature, K; ΔS _i is the change of entropy in the process of energy utilization, kJ/kg K; Q _Ri is the heat supply of steam for heating and extraction; _AR is the energy grade quantification coefficient of steam for heating and extraction; Q _R is the heat of steam for heating and extraction;

4) Determine the weight proportional coefficient of heat supply and power generation in the gas-steam combined cycle system:

X _qR ＝A _R Q _R /A _f Q _cogf

X _qP ＝A _P Q _P /A _f Q _cogf

In the formula, X _qR is the weight proportional coefficient of heating energy consumption in the system; X _qP is the weight proportional coefficient of power generation energy consumption in the system; A _f is the energy grade quantization coefficient of fuel; A _P is the energy grade quantization coefficient of electric energy; Q _cogf is the quantity of fuel combustion and chemical energy converted into heat energy, the unit is kJ; Q _P is the energy of generating electric energy, the unit is kJ;

5) Determine the final heat and electricity allocation ratio. The final heat and electricity allocation ratio is the ratio of the weight proportional coefficient of the energy consumed by heating in the system to the sum of the weight proportional coefficients of the energy consumed by power generation. The expression is as follows:

In the formula, β _tp is the final thermoelectric sharing ratio, ΔQ is the total energy loss; ΔQ _r is the energy loss allocated to the heat side, and the unit is kJ.

In order to determine the rationality of the fuel cost apportionment method for gas-steam combined cycle heat and power cogeneration units of the present invention for heat supply and power generation, the method is compared with the traditional heat and power apportionment ratio calculation method. Figures 1 to 3 show a gas-steam combined cycle heat and power cogeneration unit. The unit has three heat supply and steam extraction units. When the load rate is 100% and the ambient temperature is 27.85°C, the calculated apportionment ratio. Figures 1 to 3 are the working conditions in which only the high, medium and low pressure heating and extraction are changed, and the other two extractions are unchanged. The cascade utilization method in the figure is the apportionment method of the present invention.

Figures 1 to 3 show that the calculation results of the cascade utilization method proposed by the present invention are always between the heat method and the actual enthalpy drop method, and the characteristics of the energy grade change of the gas-steam combined heat and power unit are considered, that is, both electricity and heat The energy grades of these two energy products are different; the heat grade contained in the flue gas of the gas cycle is higher than that contained in the steam of the steam cycle; the heat grade contained in the steam entering the steam turbine is higher than that The heat-carrying steam of network heating contains the grade of heat. In addition, this method has a clear theoretical basis, which can promote the comprehensive utilization of energy cascades, use energy according to quality, and the calculation is relatively simple. It takes into account the energy cascade utilization relationship of the gas-steam combined cycle and the thermal power under specific working conditions during operation. Load combination conditions can reasonably allocate fuel costs to heating and power generation, and provide a reference for formulating heating and power generation prices.

Claims (5)

1. a kind of methodology of the heat supply of Gas-steam Combined Cycle cogeneration units and fuel used to generate electricity cost, feature exist In including the following steps:

1) according to unit practical operation situation, the value of parameter needed for calculating is determined；

2) assume unit share n sections of heat supply steam extractions, determine the energy grade quantization parameter for the heat that i-th section of heat supply steam extraction is contained with And total heat supply steam extraction energy grade quantization parameter:

In formula, for i-th section of heat supply steam extraction, A_RiFor its energy grade quantization parameter；ΔE_iDuring its energy utilization Variable quantity, kJ/kg；ΔH_iFor the enthalpy variable quantity during its energy utilization, kJ/kg；T₀For environment temperature, K；ΔS_iFor it Changes of entropy amount during energy utilization, kJ/kgK；QR_iFor the heating load of its heat supply steam extraction, kJ；A_RFor heat supply steam extraction Energy grade quantization parameter；Q_RFor the heating load of heat supply steam extraction, kJ；

3) the weight proportion coefficient in gas-steam combined cycle system for heat and generating power is determined:

X_qR=A_RQ_R/A_fQ_cogf

X_qP=A_PQ_P/A_fQ_cogf

In formula, X_qRFor the weight proportion coefficient in system for heat loss energy；X_qPFor the weight ratio of power generation consumption energy in system Example coefficient；A_fFor the energy grade quantization parameter of fuel；A_PFor the energy grade quantization parameter of electric energy；Q_cogfFor fuel combustion, change Learn the quantity that can be changed into thermal energy, kJ；Q_PFor the energy for issuing electric energy, kJ；

4) final cost allocation is determined, final cost allocation result is the weight proportion in system for heat loss energy The ratio of coefficient and itself and the sum of the weight proportion coefficient for consuming energy that generates electricity, expression formula are as follows:

In formula, β_tpFor final cost allocation；Δ Q is total energy loss, kJ；ΔQ_rFor the energy damage for distributing to heat side It loses, kJ.

2. point of Gas-steam Combined Cycle cogeneration units heat supply according to claim 1 and fuel used to generate electricity cost Booth method, it is characterised in that the loss that total energy loss Δ Q includes is as follows:

Δ Q=Δ (A_fQ_cogf)+Δ(A₃Q₃)+Δ(A_bQ_b)+Δ(A₄Q₄)+Δ(A_rQ_r)

In formula, Δ (A_fQ_cogf) it is the energy loss of natural gas in combustion；Δ(A₃Q₃) it is that flue gas does work in gas turbine The energy loss of process；Δ(A_bQ_b) be waste heat boiler in energy loss；Δ(A₄Q₄) it is steam in steam turbine acting process Energy loss；Δ(A_rQ_r) it is energy loss of the heat supply steam extraction to heat user transportational process, unit is kJ.

3. Gas-steam Combined Cycle cogeneration units heat supply according to claim 1 or 2 and fuel used to generate electricity cost Methodology, it is characterised in that by total energy loss Δ Q according to X_qRWith X_qPRatio distribute to heat supply side and power generation side:

Δ Q=Δ Q_r+ΔQ_p

In formula, Δ Q_pFor the energy loss for distributing to power generation side, kJ.

4. point of Gas-steam Combined Cycle cogeneration units heat supply according to claim 1 and fuel used to generate electricity cost Booth method, it is characterised in that the energy grade quantization parameter A of the electric energy_PIt is 1.

5. point of Gas-steam Combined Cycle cogeneration units heat supply according to claim 1 and fuel used to generate electricity cost Booth method, it is characterised in that the energy grade quantization parameter A of the fuel_fIt is 1.